Apparatus configured to report aperiodic channel state information for dual connectivity

ABSTRACT

Embodiments of a system and method for reporting channel state information (CSI) in a wireless network are generally described herein. In some embodiments, an apparatus of a User Equipment (UE) can include physical layer circuitry to receive, in a first subframe, a first aperiodic CSI request from a first cell group, and a second aperiodic CSI request from a second cell group. The UE can include processing circuitry to determine a number of requested CSI processes corresponding to the first aperiodic CSI request and the second aperiodic CSI request. Additionally, the processing circuitry can select a subset of the requested CSI processes when the determined number of requested CSI processes is more than five. Furthermore, the processing circuitry can calculate CSI for the selected CSI processes.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.14/741,233, filed Jun. 16, 2015, now issued as U.S. Pat. No. 9,730,258,which claims priority under 35 U.S.C. 119(e) to U.S. Provisional PatentApplication Ser. No. 62/084,997, filed Nov. 26, 2014, and U.S.Provisional Patent Application Ser. No. 62/081,281, filed Nov. 18, 2014,each of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

Embodiments pertain to radio access networks. Some embodiments relate toaperiodic channel state information (CSI) processing and reporting incellular networks, such as Long Term Evolution (LTE) and LTE advanced(LTE-A) networks.

BACKGROUND

Current issues with communicating data over a wireless network caninclude low throughput, frequent handovers, handover failures,inefficient offloads, and service interruptions.

Dual connectivity in an LTE network can significantly improve per-userthroughput, reduce handovers, and reduce handover failures by allowing auser to be connected simultaneously to a master cell group and asecondary cell group via a macro evolved Node B (eNB) and a small celleNB.

With regards to low throughput, dual connectivity can increase per-userthroughput by aggregating radio resources from at least two eNBs.Additionally, throughput can be increased by transmitting or receivingmultiple streams and dynamically adapting to the best radio conditionsof multiple cells. Also, small cell eNBs can provide additional capacityfor user equipments (UEs) having multiple radio connections.

Moreover, moving UEs suffer frequent handover failure, inefficientoffload, and service interruption. The consequences are more severe ifthe UE's velocity is higher and cell coverage is smaller. Dualconnectivity can reduce the handover failure rate by maintaining themacro eNB (e.g., primary cell) connection as the coverage layer. Dualconnectivity also helps in load balancing between the macro eNB and thesmall cell eNB (e.g., secondary cell).

Furthermore, dual connectivity can reduce signaling overhead towards thecore network due to frequent handover. For example, signaling overheadcan be reduced by not issuing handover operations as long as the UE iswithin macro coverage.

However, dual connectivity can impose several technical challenges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of a 3rd Generation Partnership Project(3GPP) network, in accordance with some embodiments;

FIG. 2 is a functional diagram of a User Equipment (UE), in accordancewith some embodiments;

FIG. 3 is a functional diagram of an Evolved Node B (eNB), in accordancewith some embodiments;

FIG. 4 illustrates an example of a heterogeneous network for a dualconnectivity implementation, in accordance with some embodiments;

FIG. 5 illustrates an example scenario of dual connectivityimplementation, in accordance with some embodiments;

FIG. 6 illustrates an example of channel state information (CSI)attributes used for prioritizing CSI process calculations, in accordancewith some embodiments;

FIG. 7 illustrates the operation of a method performed by a UE forcalculating prioritized CSI processes for a CSI report based on two CSIaperiodic requests received in the same subframe; and

FIG. 8 illustrates the operation of a method performed by an eNB forselecting a transmission mode based on the CSI report received from theUE, in accordance with some embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

In this disclosure, embodiments are often discussed with reference tomacro eNBs and small cell eNBs. A small cell eNB can be a pico eNB.Additionally, various embodiments disclosed herein are applicable inother settings with other terminology. For example, a macro eNB can bedenoted as an “anchor eNB,” “primary eNB,” or “master eNB,” while asmall cell eNB can be denoted as an “assisting eNB,” “secondary eNB,” or“slave eNB”.

FIG. 1 is a functional diagram of a 3GPP network, in accordance withsome embodiments. The network comprises a radio access network (RAN)(e.g., as depicted, the E-UTRAN or evolved universal terrestrial radioaccess network) 100 and a core network 120 (e.g., shown as an evolvedpacket core (EPC)) coupled together through an S1 interface 115. For thesake of convenience and brevity, only a portion of the core network 120,as well as the RAN 100, is shown.

The core network 120 includes a mobility management entity (MME) 122, aserving gateway (serving GW) 124, and a packet data network gateway (PDNGW) 126. The RAN 100 includes Evolved Node-Bs (eNBs) 104 (which canoperate as base stations) for communicating with User Equipments (UEs)102. The eNBs 104 can include macro eNBs and low power (LP) eNBs, suchas micro eNBs.

The MME 122 is similar in function to the control plane of legacyServing GPRS Support Nodes (SGSN). The MME 122 manages mobility aspectsin access, such as gateway selection and tracking area list management.The serving GW 124 terminates the interface toward the RAN 100, androutes data packets between the RAN 100 and the core network 120. Inaddition, the serving GW 124 may be a local mobility anchor point forinter-eNB handovers and also may provide an anchor for inter-3GPPmobility. Other responsibilities may include lawful intercept, charging,and some policy enforcement. The serving GW 124 and the MME 122 may beimplemented in one physical node or separate physical nodes. The PDN GW126 terminates an SGi interface toward a packet data network (PDN). ThePDN GW 126 routes data packets between the core network 120 and theexternal PDN, and may be a key node for policy enforcement and chargingdata collection. It can also provide an anchor point for mobility withnon-LTE accesses. The external PDN can be any kind of IP network, aswell as an IP Multimedia Subsystem (IMS) domain. The PDN GW 126 and theserving GW 124 may be implemented in one physical node or separatephysical nodes.

The eNBs 104 (macro and micro) terminate the air interface protocol andmay be the first point of contact for a UE 102. In some embodiments, aneNB 104 can fulfill various logical functions for the RAN 100, includingbut not limited to RNC (radio network controller) functions such asradio bearer management, uplink and downlink dynamic radio resourcemanagement and data packet scheduling, and mobility management. Inaccordance with embodiments, the UEs 102 may be configured tocommunicate orthogonal frequency-division multiplexing (OFDM)communication signals with an eNB 104 over a multicarrier communicationchannel in accordance with an orthogonal frequency-division multipleaccess (OFDMA) communication technique. The OFDM signals may comprise aplurality of orthogonal subcarriers.

The S1 interface 115 is the interface that separates the RAN 100 and thecore network 120. It is split into two parts: the S1-MME, which carriesdata traffic between the eNBs 104 and the serving GW 124, and theS1-MME, which is a signaling interface between the eNBs 104 and the MME122. The X2 interface is the interface between eNBs 104. The X2interface comprises two parts, the X2-C and X2-U. The X2-C is thecontrol plane interface between the eNBs 104, while the X2-U is the userplane interface between the eNBs 104.

In cellular networks, LP cells are typically used to extend coverage toindoor areas where outdoor signals do not reach well, or to add networkcapacity in areas with very dense phone usage, such as train stations.As used herein, the term “low power (LP) eNB” refers to any suitablerelatively low power eNB for implementing a narrower cell (narrower thana macro cell), such as a femtocell, a picocell, or a micro cell.Femtocell eNBs are typically provided by a mobile network operator toits residential or enterprise customers. A femtocell is typically thesize of a residential gateway or smaller and generally connects to theuser's broadband line. Once plugged in, the femtocell connects to themobile operator's mobile network and provides extra coverage in atypical range of 30 to 50 meters for residential femtocells. Thus, an LPeNB might be a femtocell eNB since it is coupled through the PDN GW 126.Similarly, a picocell is a wireless communication system typicallycovering a small area, such as in-building (offices, shopping malls,train stations, etc.), or more recently in-aircraft. A picocell eNB cangenerally connect through the X2 link to another eNB such as a macro eNBthrough its base station controller (BSC) functionality. Thus, an LP eNBmay be implemented with a picocell eNB since it is coupled to a macroeNB via an X2 interface. Picocell eNBs or other LP eNBs may incorporatesome or all functionality of a macro eNB. In some cases, an LP eNB maybe referred to as an “access point base station” or “enterprisefemtocell.”

In some embodiments, a downlink resource grid may be used for downlinktransmissions from an eNB 104 to a UE 102, while uplink transmissionsfrom the UE 102 to the eNB 104 may utilize similar techniques. The gridmay be a time-frequency grid, called a “resource grid” or“time-frequency resource grid,” which is the physical resource in thedownlink in each slot. Such a time-frequency plane representation iscommon for OFDM systems, which makes it intuitive for radio resourceallocation. Each column and each row of the resource grid correspond toone OFDM symbol and one OFDM subcarrier, respectively. The duration ofthe resource grid in the time domain corresponds to one slot in a radioframe. The smallest time-frequency unit in a resource grid is denoted asa “resource element.” Each resource grid comprises a number of resourceblocks, which describe the mapping of certain physical channels toresource elements. Each resource block comprises a collection ofresource elements in the frequency domain and may represent the smallestquanta of resources that currently can be allocated. There are severaldifferent physical downlink channels that are conveyed using suchresource blocks. With particular relevance to this disclosure, two ofthese physical downlink channels are the physical downlink sharedchannel and the physical downlink control channel.

The physical downlink shared channel (PDSCH) carries user data andhigher-layer signaling to a UE 102. The physical downlink controlchannel (PDCCH) or enhanced downlink control channel (EPDCCH) carriesinformation about the transport format and resource allocations relatedto the PDSCH channel, among other things. It also informs the UE 102about the transport format, resource allocation, and hybrid automaticrepeat request (HARQ) information related to the uplink shared channel.Typically, downlink scheduling (assigning control and shared channelresource blocks to UEs 102 within a cell) is performed at the eNB 104based on channel quality information fed back from the UEs 102 to theeNB 104, and then the downlink resource assignment information is sentto a UE 102 on the control channel (PDCCH) used for (assigned to) the UE102.

The PDCCH uses control channel elements (CCEs) to convey the controlinformation. Before being mapped to resource elements, the PDCCHcomplex-valued symbols are first organized into quadruplets, which arethen permuted using a sub-block inter-leaver for rate matching. EachPDCCH is transmitted using one or more of these CCEs, where each CCEcorresponds to nine sets of four physical resource elements known asresource element groups (REGs). Four quadrature phase-shift keying(QPSK) symbols are mapped to each REG. The PDCCH can be transmittedusing one or more CCEs, depending on the size of downlink controlinformation (DCI) and the channel condition. There may be four or moredifferent PDCCH formats defined in LTE with different numbers of CCEs(e.g., aggregation level L=1, 2, 4, or 8).

FIG. 2 is a functional diagram of a User Equipment (UE) 200, inaccordance with some embodiments. FIG. 3 is a functional diagram of anEvolved Node B (eNB) 300, in accordance with some embodiments. It shouldbe noted that in some embodiments, the eNB 300 can be a stationarynon-mobile device. The UE 200 can be a UE 102 as depicted in FIG. 1,while the eNB 300 can be an eNB 104 as depicted in FIG. 1. The UE 200can include physical layer circuitry (PHY) 202 for transmitting andreceiving signals to and from the eNB 300, other eNBs, other UEs, orother devices, using one or more antennas 201. The eNB 300 can includephysical layer circuitry (PHY) 302 for transmitting and receivingsignals to and from the UE 200, other eNBs, other UEs, or other devices,using one or more antennas 301.

The UE 200 can also include medium access control layer (MAC) circuitry204 for controlling access to the wireless medium, while the eNB 300 canalso include medium access control layer (MAC) circuitry 304 forcontrolling access to the wireless medium.

The UE 200 can also include processing circuitry 206 and memory 208arranged to perform the operations described herein, and the eNB 300 canalso include processing circuitry 306 and memory 308 arranged to performthe operations described herein.

The eNB 300 can also include one or more interfaces 310, which canenable communication with other components, including other eNBs 104(FIG. 1), components in the core network 120 (FIG. 1), or other networkcomponents. In addition, the interfaces 310 may enable communicationwith other components that may not be shown in FIG. 1, includingcomponents external to the network. The interfaces 310 may be wired,wireless, or a combination thereof.

The antennas 201, 301 may comprise one or more directional oromnidirectional antennas, including, for example, dipole antennas,monopole antennas, patch antennas, loop antennas, microstrip antennas,or other types of antennas suitable for transmission of radio frequency(RF) signals. In some multiple-input multiple-output (MIMO) embodiments,the antennas 201, 301 may be effectively separated to take advantage ofspatial diversity and the different channel characteristics that mayresult.

In some embodiments, mobile devices or other devices described hereinmay be part of a portable wireless communication device, such as apersonal digital assistant (PDA), a laptop or portable computer withwireless communication capability, a web tablet, a wireless telephone, asmartphone, a wireless headset, a pager, an instant messaging device, adigital camera, an access point, a television, a medical device (e.g., aheart rate monitor, a blood pressure monitor, etc.), or another device,including wearable devices that may receive and/or transmit informationwirelessly. In some embodiments, the mobile device or other device canbe a UE or an eNB configured to operate in accordance with 3GPPstandards. In some embodiments, the mobile device or other device may beconfigured to operate according to other protocols or standards,including IEEE 802.11 or other IEEE standards. In some embodiments, themobile device or other device may include one or more of a keyboard, adisplay, a non-volatile memory port, multiple antennas, a graphicsprocessor, an application processor, speakers, and other mobile deviceelements. The display may be an LCD screen including a touch screen.

Although the UE 200 and the eNB 300 are each illustrated as havingseveral separate functional elements, one or more of the functionalelements can be combined and can be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements can comprise one or more microprocessors, DSPs,field-programmable gate arrays (FPGAs), application specific integratedcircuits (ASICs), radio-frequency integrated circuits (RFICs), andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements can refer to one or more processes operating on oneor more processing elements.

Embodiments can be implemented in one or a combination of hardware,firmware, and software. Embodiments can also be implemented asinstructions stored on a computer-readable storage device, which can beread and executed by at least one processor to perform the operationsdescribed herein. A computer-readable storage device can include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a computer-readable storagedevice can include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media. Some embodiments caninclude one or more processors that can be configured with instructionsstored on a computer-readable storage device.

In some embodiments, the UE 200 can be configured to receive OFDMcommunication signals over a multicarrier communication channel inaccordance with an OFDMA communication technique. The OFDM signals cancomprise a plurality of orthogonal subcarriers. In some broadbandmulticarrier embodiments, the eNB 300 can be part of a broadbandwireless access (BWA) communication network, such as a WorldwideInteroperability for Microwave Access (WiMAX) communication network, a3rd Generation Partnership Project (3GPP) Universal Terrestrial RadioAccess Network (UTRAN) Long-Term-Evolution (LTE) network, or aLong-Term-Evolution (LTE) communication network, although the scope ofthis disclosure is not limited in this respect. In these broadbandmulticarrier embodiments, the UE 200 and the eNB 300 can be configuredto communicate in accordance with an OFDMA technique.

FIG. 4 illustrates an example of a heterogeneous network 400 for a dualconnectivity implementation, according to some embodiments. FIG. 4illustrates an example of different deployments that includes a largecell representing a macro cell 410. The heterogeneous network 400 canalso include a small cell 420 (e.g., micro cell) in the same frequencyas the macro layer, which includes the macro cell 410. Additionally, theheterogeneous network 400 can include small cells 430 deployed inclusters and small cells deployed in non-clusters (e.g., spread in acity) in a frequency layer different from that of the macro cell 410.Furthermore, the heterogeneous network 400 can include beamforming smallcells 440 in a different radio access technology (RAT) which aredeployed with beamforming ability.

Accordingly, in such a heterogeneous network 400, dual connectivity canallow the UE 102 to connect simultaneously to the macro cell 410 and thesmall cells 430 in a frequency layer different from the macro cell 410.

As previously mentioned, dual connectivity in an LTE network cansignificantly improve per-user throughput, reduce handovers, and reducehandover failures by allowing a user to be connected simultaneously tothe macro cell 410 and small cells (e.g., small cell 420, small cell430, and/or small cell 440).

FIG. 5 illustrates an example of a scenario 500 of a dual connectivityimplementation, in accordance with some embodiments. In dualconnectivity, the serving cells are operated in different eNBs. Forexample, the primary cell is served from a macro cell 510 and asecondary cell is served from a small cell (e.g., a first small cell520, and/or a second small cell 530). In some instances, the small cellcan be a pico cell or a femto cell. For example, the first small cell520 is a first pico cell, and the second small cell 530 is a second picocell.

As previously mentioned, one of the motivations of dual connectivity isto avoid frequent handovers in heterogeneous deployment, as illustratedin FIG. 4. As shown in the scenario 500, the UE 102 can move within acoverage area 560 of the macro cell 510. Since the coverage area (notpictured) of each of the small cells (e.g., coverage of first small cell520 and second small cell 530) is smaller than that of the macro cell510, the UE 102 may need to be handed over to the macro cell 510 oranother small cell if the UE is connected to the small cell only. On theother hand, if the UE is connected to the macro cell 510, handover isnot required, but offloading to the small cell is not provided. Toachieve offloading and avoid the frequent handover, carrier aggregationcan be performed.

With carrier aggregation, the UE can be served by both the macro cell510 operating at a first frequency 540, and the small cell (e.g., firstsmall cell 520, and/or second small cell 530) operating at a secondfrequency 550. For example, the primary cell can be the macro cell 510and the secondary cell can be the small cell (e.g., first small cell520, second small cell 530).

For example, at T₁, the UE 102, being within the coverage area (e.g.,coverage area 560) of the macro cell 510, can be served by the macrocell 510 as the primary cell. Then at T₂, when the UE 102 is within thecoverage area of the macro cell 510 and the first small cell 520, thefirst small cell 520 can be added as a secondary cell while the macrocell 510 is maintained as the primary cell. Additionally, at T₃, whenthe UE 102 is within the coverage area of the macro cell 510 but movesout of the coverage area of the first small cell 520, the first smallcell 520 can be removed as the secondary cell while the macro cell 510is maintained as the primary cell. Subsequently at T₄, when the UE 102is within the coverage area of the macro cell 510 and the second smallcell 530, the second small cell 530 can be added as a secondary cellwhile the macro cell 510 is maintained as the primary cell. Finally atT₅, when the UE 102 is within the coverage area of the macro cell 510but moves out of the coverage area of the second small cell 530, thesecond small cell 530 can be removed as the secondary cell while themacro cell 510 is maintained as the primary cell.

In the example in FIG. 5, the primary cell (e.g., macro cell 510) can beresponsible for mobility management, and therefore the UE 102 does notneed to be handed over as long as the UE 102 is moving within thecoverage area of the macro cell 510. Additionally, the secondary cell(e.g., first small cell 520, second small cell 530) can be used for datatransmission, and the UE can take advantage of offloading to thesecondary cell. The change from the first small cell 520 to second smallcell 530 may be supported with secondary cell addition or removal,instead of handover.

In the scenario illustrated in FIG. 5, an example of a differencebetween dual connectivity and LTE Rel-10 carrier aggregation isillustrated. For example, in dual connectivity, the macro cell (e.g.,macro cell 510) and the small cell (e.g., first small cell 520, secondsmall cell 530) are served by different eNBs 104 and the two cells areconnected through an X2 interface. In LTE Rel-10 carrier aggregation, itcan be assumed that all serving cells are served by the same eNB 104.

Given that the macro cell (e.g., macro cell 510) and the small cell(e.g., first small cell 520, second small cell 530) are served bydifferent eNBs 104, it is possible that the UE 102 receives more thanone aperiodic CSI request in the same subframe from both the macro celland the small cell. FIGS. 6-8 illustrate techniques for prioritizing andcalculating CSI processes when multiple aperiodic CSI requests arereceived in the same subframe.

Additionally, in some embodiments, LTE carrier aggregation can bedeployed on top of dual connectivity. For example, the macro and/or picoeNB 104 may aggregate multiple component carriers (or cells) in downlinkand/or uplink channels.

Channel State Information (CSI) Reporting

LTE-Advanced (LTE-A) can support two types of CSI reporting, which areperiodic and aperiodic reporting. Periodic CSI reporting may be mainlyused to indicate the channel quality of the downlink channel at the UE102 on a long-term basis. Periodic CSI can be provided by the UE 102 inaccordance with a predefined reporting time schedule configured by theserving cell using higher-layer signaling (e.g. Radio Resource Control(RRC)) and usually has low overhead.

In contrast, aperiodic CSI reporting can be used to provide larger andmore detailed reporting in a single reporting instance based on adynamic CSI request triggered by the serving cell using a CSI requestfiled in the downlink control information (DCI). The DCI can include aPhysical Downlink Control Channel (PDCCH) or an enhanced PhysicalDownlink Control Channel (EPDCCH).

In transmission mode 10, multiple CSI reports corresponding to multipleCSI processes on the same serving frequency can be requested by the eNB104 in accordance with the Table 7.2.1-1B defined in TS 36.213 Rel-11(reproduced below). The set of CSI processes for reporting correspondingto CSI request fields “01”, “10”, and “11” are configured using RRCsignaling.

TABLE 7.2.1-1B CSI Request field for PDCCH/EPDCCH with uplink DCI formatin UE specific search space Value of CSI request field Description ‘00’No aperiodic CSI report is triggered ‘01’ Aperiodic CSI report istriggered for a set of CSI process(es) configured by higher layers forserving cell C ‘10’ Aperiodic CSI report is triggered for a 1^(st) setof CSI process(es) configured by higher layers ‘11’ Aperiodic CSI reportis triggered for a 2^(nd) set of CSI process(es) configured by higherlayers

In carrier aggregation mode, multiple CSI reports corresponding tomultiple downlink cells can be requested by the eNB 104 in accordancewith the Table 7.2.1-1A defined in TS 36.213 Rel-10 (reproduced below).The set of serving cells for reporting corresponding to CSI requestfields “10” and “11” are configured using RRC signaling.

TABLE 7.2.1-1A CSI Request field for PDCCH/EPDCCH with uplink DCI formatin UE specific search space Value of CSI request field Description ‘00’No aperiodic CSI report is triggered ‘01’ Aperiodic CSI report istriggered for serving cell C ‘10’ Aperiodic CSI report is triggered fora 1^(st) set of serving cells configured by higher layers ‘11’ AperiodicCSI report is triggered for a 2^(nd) set of serving cells configured byhigher layers

Given that the UE 102 is not expected to receive more than one CSIrequest in one downlink subframe as defined in Section 7.2.1 of TS36.211, the maximum number of CSI reports generated by the UE 102 in onesubframe can be limited to five.

In the case of carrier aggregation, the maximum number of CSI requestsis five due to an ideal backhaul link and a limit of one CSI request perdownlink subframe. As previously mentioned, In LTE Rel-10 carrieraggregation, it can be assumed that all serving cells are served by thesame eNB 104.

However, with dual connectivity, the macro cell (e.g., macro cell 510)and the small cell (e.g., first small cell 520, second small cell 530)are served by different eNBs 104 and two cells are connected through anX2 interface. Therefore, it can be possible for more than one CSIrequest to be sent in one downlink subframe. Additionally, with regardsto dual connectivity, which can have a non-ideal backhaul link with highand variable delays, it can be difficult to ensure that only one CSIrequest is sent in each downlink subframe.

Furthermore, due to the CSI computational complexity, it is desirable tokeep CSI calculation at the UE 102 at a reasonable level. Therefore, insome instance, a predetermined number of CSI reports to be calculated bythe UE 102 can be set. For example, the predetermined number of CSIreports can be set to five, which is the existing constraint on themaximum number of CSI reports. In this disclosure, several embodimentsare set forth that limit the number of CSI processes to be computed andreported in any subframe to five. For example, the CSI processes areprioritized and the top five CSI processes are calculated by the UE 102.

According to some embodiments, various aperiodic CSI reporting processesdisclosed herein enable a reduction in CSI computational complexity atthe UE 102 when dual connectivity is used.

FIG. 6 illustrates an example of CSI attributes 600, in accordance withsome embodiments. For example, when more than five CSI processes arerequested during the same subframe, the CSI attributes 600 can be usedto select (e.g., prioritize) the top five CSI processes for the UE 102to calculate. The CSI attributes can include, but are not limited to, acell group index 610, a CSI process index 620, a component carrier (CC)index 630, and a CSI subframe index 640. The cell group index 610 caninclude an index value corresponding to a macro cell 612 and an indexvalue corresponding to a small cell 614.

In a first set of embodiments, when simultaneous aperiodic CSI requestsare received by the UE 102 from a primary eNB and a secondary eNB, theCSI (e.g., CSI process) computational priorities may be defined based onpredetermined rules.

For example, For N total CSI processes requested in a given subframe,withN>5, the UE 102 may update a predetermined number (e.g., five) oftop priority CSI processes. Additionally, the remaining (e.g., N−5 whenthe predetermined number is five) lower-priority CSI processes may notbe updated. In some instances, a default value can be used for theremaining (e.g., non-updated) CSI processes. Alternatively, a previouslycalculated value can be used for the remaining CSI processes.

The CSI process priority list can be defined based on the CSI attributes600, such as the cell group index 610 (e.g., Type of eNB), the CSIprocess index 620, the CC index 630, and the CSI subframe index 640.

Examples of possible ordering of the priorities (starting with thehigher priority) can be defined as follows:

-   -   Cell group index 610>CSI process index 620>CC index 630>CSI        subframe index 640;    -   CSI process index 620>Cell group index 610>CC index 630>CSI        subframe index 640;    -   CSI process index 620>CC index 630>Cell group index 610>CSI        subframe index 640    -   CSI process index 620>CC index 630>CSI subframe index 640>Cell        group index 610

In one example, a lower cell group index 610 value (e.g., index valuecorresponding to a small cell 614) can have a higher priority for CSIcomputation than a higher cell group index 610 value (e.g., index valuecorresponding to a macro cell 612). Alternatively, in another example, alower cell group index 610 value can have a lower priority for CSIcomputation than a higher cell group index 610 value. In someembodiments, the macro cell 612 may be included in a cluster of macrocells that operates in a different frequency band than the small cell614 or another macro cell.

In some instances, all CSI requests for CSI processes may be reported,but not all of them may be updated. The non-updated CSI reports can be apreviously reported CSI report based on previously received aperiodicCSI data or a default value. For example, the default values can be achannel quality indicator (CQI) with an index value of “0,” which cancorrespond to an indication of the UE 102 being out of range.Additionally, a CQI with an index value of “0” can indicate that the UE102 has not received any usable LTE signals. Furthermore, the aperiodicCSI configuration (i.e., the configuration of CSI request fields fordifferent UEs 102) may be exchanged over an X2 interface between theprimary eNB and the secondary eNB.

In a second set of embodiments, the sum of the maximum number of CSIprocesses configured for each CSI request field by the primary eNB andthe secondary eNB may not exceed a predetermined number (e.g., five) ofCSI processes.

In a third set of embodiments, different CSI subframes may be used bythe primary eNB and the secondary eNB for aperiodic CSI triggering. Thesubframes used for triggering by the primary eNB may not be used foraperiodic CSI triggering by the secondary eNB. The subframes can becoordinated between the primary eNB and the secondary eNB using bitmapsignaling, which for the frequency division duplexing (FDD) case, mayhave a length of 40 bits.

FIG. 7 illustrates the operation of a method 700 for calculating CSI forselected CSI processes, in accordance with some embodiments. Asillustrated in FIGS. 5 and 6, multiple CSI requests can be received inthe same subframe, which can result in more than five requested CSIprocesses needing to be calculated by the UE 102. In such cases, aselected subset of requested CSI processes are calculated based on theCSI attributes 600. Embodiments are not limited to these configurations,however, and some or all of the techniques and operations describedherein may be applied to systems or networks that exclusively use macrocells or micro cells.

It is important to note that embodiments of the method 700 may includeadditional or even fewer operations or processes in comparison to whatis illustrated in FIG. 7. In addition, embodiments of the method 700 arenot necessarily limited to the chronological order that is shown in FIG.7. In describing the method 700, reference may be made to FIGS. 1-6,although it is understood that the method 700 may be practiced with anyother suitable systems, interfaces, and components. For example,reference may be made to the scenario 500 in FIG. 5 (described earlier)for illustrative purposes, but the techniques and operations of themethod 700 are not so limited.

In addition, while the method 700 and other methods described herein mayrefer to eNBs 104 or UEs 102 operating in accordance with 3GPP or otherstandards, embodiments of those methods are not limited to just thoseeNBs 104 or UEs 102 and may also be practiced by other mobile devices,such as a Wi-Fi access point (AP) or user station (STA). Moreover, themethod 700 and other methods described herein may be practiced bywireless devices configured to operate in other suitable types ofwireless communication systems, including systems configured to operateaccording to various IEEE standards such as IEEE 802.11.

At operation 710 of the method 700, the UE 102 receives, in a firstsubframe, a first aperiodic CSI request from a first cell group. Thephysical layer circuitry 202 (in FIG. 2) can receive the first aperiodicCSI request from an eNB (e.g., eNB 104). The first cell group can beserved by a primary eNB. The first cell group can include the macro cell510.

As described in Table 7.2.1-1B above, the request field value for thefirst aperiodic CSI request can be “01”, “10”, or “11” in thetransmission mode 10.

As described in Table 7.2.1-1A above, the request field value for thefirst aperiodic CSI request can be “10”, or “11” in the carrieraggregation mode.

Dual connectivity in an LTE network allows the UE 102 to be connectedsimultaneously to a primary cell group and a secondary cell group via aprimary eNB and a secondary eNB. As a result, in some instances, the UE102 can receive more than one aperiodic CSI request in the samesubframe. For example, the UE 102 can receive a CSI request from theprimary eNB at operation 710 and another CSI request from the secondaryeNB in the same subframe at operation 720.

At operation 720, the UE 102 receives, in the first subframe, a secondaperiodic CSI request from a second cell group. The physical layercircuitry 202 can receive the second aperiodic CSI request from anothereNB 104. The second cell group can be served by a secondary eNB. Thesecond cell group can include the first small cell 520 or the secondsmall cell 530. Additionally, the second cell group can operate at adifferent frequency than the first cell group.

As described in Table 7.2.1-1B above, the request field value for thesecond aperiodic CSI request can be “01”, “10”, or “11” in thetransmission mode 10.

As described in Table 7.2.1-1A above, the request field value for thesecond aperiodic CSI request can be “10”, or “11” in the carrieraggregation mode.

In some instances, the first aperiodic CSI request and the secondaperiodic CSI request are received in the first subframe when the firstaperiodic CSI request is received within 33 microseconds of the secondaperiodic CSI request.

In one example, the first cell group includes a macro eNB and the secondcell group includes a small cell eNB. In another example, the first cellgroup includes a small cell eNB and the second cell group includes amacro eNB. In yet another example, the first cell group and the secondcell group can include different macro eNBs operating at differentfrequencies. In yet another example, the first cell group and the secondcell group can include different small cell eNBs operating at differentfrequencies.

At operation 730, the UE 102 determines a number of requested CSIprocesses corresponding to the first aperiodic CSI request and thesecond aperiodic CSI request. In some instances, the processingcircuitry 206 (in FIG. 2) determines the number of requested CSIprocesses. The number of requested CSI processes can be determining byadding the number of CSI processes associated with the first aperiodicCSI request and the number of CSI processes associated with the secondaperiodic CSI request. As previously mentioned, due to the CSIcomputational complexity, the number of CSI processes to be computed andreported in any subframe may be limited to predetermined number (e.g.,five) of CSI processes.

At operation 740, the UE 102 selects a subset of the requested CSIprocesses when the determined number of requested CSI processes is morethan a predetermined number (e.g., five). For example, the UE 102 canselect a subset of the requested CSI processes when there are more thanfive requested CSI processes. In some instances, the processingcircuitry 206 selects the subset of CSI processes for updating (e.g.,calculating). The number of requested CSI processes is determined atoperation 730.

In some instances, the selected CSI processes comprise a total of fiveCSI processes. For example, the CSI processes are prioritized and thetop five CSI processes are selected by the UE 102.

In some instances, the selected CSI processes comprise at least onefewer CSI process than the requested CSI processes. For example, whenthe number of requested CSI processes is seven, the number of selectedCSI processes is 6 or less.

In some instances, the processing circuitry 206 is further configured togenerate a priority list of the requested CSI processes based on CSIattributes. Additionally, the selecting of the subset of the requestedCSI processes at operation 740 can be based on the priority list. TheCSI attributes can include the CSI attributes 600 of FIG. 6. The CSIattributes 600 include the cell group index 610, the CSI process index620, the CC index 630, and the CSI subframe index 640.

The priority list can be preset by a UE (e.g., UE 102) or an eNB (e.g.,eNB 104). In some instances, the CSI process index 620 can have a higherpriority in the priority list than the CC index 630. In some instances,the CC index 630 can have a higher priority in the priority list thanthe CSI subframe index 640.

In some instances, a lower cell group index 610 may have a higherpriority in the priority list than a higher cell group index 610.Alternatively, the lower cell group index 610 may have a lower priorityin the priority list than the higher cell group index 610. The lowercell group index 610 can correspond to a small cell eNB or secondaryeNB. The higher cell group index 610 can correspond to a macro eNB orprimary eNB.

At operation 750, the UE 102 calculates CSI for the selected CSIprocesses from operation 740. The processing circuitry 206 can calculatethe CSI for each selected CSI process. As previously mentioned, a totalof five CSI processes can be selected at operation 740, and thereforeCSI for five processes can be calculated at operation 750.

The calculated CSI can include a precoding matrix indicator value. Asdescribed in method 800, a transmission parameter that is set ortransmitted by a eNB 104 can include a precoding weight for transmittingantennas of eNB that is based on the precoding matrix indicator value.

Additionally, the calculated CSI can include a Rank Indicator (RI)value. The number of layers determined by the eNB 104 in method 800 isbased on the RI value.

Furthermore, the calculated CSI can include a Channel Quality Indicator(CQI) value. A modulation and coding scheme (MCS) determined by the eNB104 in method 800 can be based on the CQI value.

In some instances, the method 700 can further include generating a firstCSI report and a second CSI report. For example, the CSI reports can begenerated using the processing circuitry 206. The first CSI report caninclude the calculated CSI, from operation 750, corresponding to thefirst aperiodic CSI request. The second CSI report can include thecalculated CSI, from operation 750, corresponding to the secondaperiodic CSI request.

Additionally, the method 700 can further include transmitting the firstCSI report to the first cell group, and the second CSI report to thesecond cell group. As previously mentioned, the first cell group sentthe first aperiodic CSI request at operation 710, and the second cellgroup sent the second aperiodic CSI request at operation 720. Forexample, the physical layer circuitry 202 can transmit the first CSIreport to the first cell group, and transmit the second CSI report tothe second cell group.

Furthermore, all of the requested CSI processes from the first andsecond aperiodic requests are included in the first CSI report or secondCSI report, but CSI is only calculated for the CSI processes selected atoperation 740.

In some instances, the processing circuitry 206 is further configured toaccess previously stored CSI for a remaining process, the remainingprocess being different from the CSI processes selected at operation740. Additionally, the first CSI report or the second CSI report caninclude the accessed CSI for the remaining process. For example, aremaining CSI process is a CSI process that is not updated (e.g.,calculated) at operation 750. The processing circuitry 206 can accessthe value of the remaining CSI process stored in the memory 208. Thevalue can correspond to previously calculated CSI associated with theremaining CSI process.

In some instances, the processing circuitry 206 is further configured togenerate generic CSI for the remaining process. As previously mentioned,the remaining process is different from the CSI processes selected atoperation 740. Additionally, the generic CSI indicates that theremaining process has not been calculated. Furthermore, the first CSIreport or the second CSI report can include the generic CSI for theremaining process. For example, the portion of the first CSI reportassociated with the remaining process includes a Channel QualityIndicator (CQI) value that is set to zero to indicate that the CQI hasnot been calculated.

In some instances, the processing circuitry 206 is further configured togenerate a CSI report based on the calculated CSI for the selectedprocesses. Additionally, the physical layer circuitry 202 is furtherconfigured to transmit the CSI report to the first cell group and thesecond cell group.

FIG. 8 illustrates the operation of a method 800 for selecting atransmission mode based on the calculated CSI, in accordance with someembodiments. It is important to note that embodiments of the method 800may include additional or even fewer operations or processes incomparison to what is illustrated in FIG. 8. In addition, embodiments ofthe method 800 are not necessarily limited to the chronological orderthat is shown in FIG. 8. In describing the method 800, reference may bemade to FIGS. 1-7, although it is understood that the method 800 may bepracticed with any other suitable systems, interfaces, and components.

In addition, while the method 800 and other methods described herein mayrefer to eNBs 104 or UEs 102 operating in accordance with 3GPP or otherstandards, embodiments of those methods are not limited to just thoseeNBs 104 or UEs 102 and may also be practiced by other mobile devices,such as a Wi-Fi access point (AP) or user station (STA). Moreover, themethod 800 and other methods described herein may be practiced bywireless devices configured to operate in other suitable types ofwireless communication systems, including systems configured to operateaccording to various IEEE standards such as IEEE 802.11.

The method 800 can be performed by an eNB 104 for selecting atransmission mode for a UE (e.g., UE 102) having dual connectivity inheterogeneous network.

At operation 810, the eNB 104 can send an aperiodic CSI request to a UE102. In some instances, the physical layer circuitry 302 can send theCSI request.

In some instances, different CSI subframes may be used by the primaryeNB and the secondary eNB for aperiodic CSI triggering. The subframesused for aperiodic CSI triggering by the primary eNB may not be used foraperiodic CSI triggering by the secondary eNB. The subframes can becoordinated between the primary eNB and the secondary eNB using bitmapsignaling, which for the frequency division duplexing (FDD) case, mayhave a length of 40 bits. Additionally, each bit can correspond to adownlink subframe, where a “1” indicates that triggering may be used anda “0” indicates that triggering may not be used.

At operation 820, the PHY 302 of the eNB 104 can receive a CSI reportbased on the aperiodic request sent at operation 810. The CSI report canbe generated and sent by the UE 102 using the method 700 in FIG. 7. Insome instances, the physical layer circuitry 302 of the eNB 300 canreceive the CSI report.

The CSI report can include CSI for selected CSI processes calculated atoperation 750. Additionally, the CSI processes can be selected by the UE102 at operation 740. Furthermore, the CSI report can include genericCSI for a remaining process. The remaining process can be a CSI processnot selected at operation 740, but requested in the aperiodic CSIrequest sent at operation 810.

At operation 830, the eNB 104 can determine that the remaining CSIprocess has not been calculated based on the generic CSI. In someinstances, operation 830 can be performed by the processing circuitry306 of the eNB 300.

At operation 840, the processing circuitry 306 of the eNB 104 can selecta transmission parameter based on the calculated CSI for the selectedCSI processes in the CSI report. In some instances, operation 840 can beperformed by the processing circuitry 306 of the eNB 300.

The transmission parameter(s) may be received at the UE 102. Thetransmission parameters may be set or transmitted by one of the eNBs104, such as the eNB 104 of the serving cell. Accordingly, the decisionof the eNB 104 to indicate the transmission mode may be based at leastpartly on information included in the CSI report previously described.

In some instances, the transmission parameters include a precodingweight for transmitting antennas of eNB that is based on a precodingmatrix indicator value in the calculated CSI for one of the selected CSIprocesses.

In some instances, the transmission parameters include a number oflayers that is based on the Rank Indicator (RI) value in the calculatedCSI for one of the selected CSI processes.

In some instances, the transmission parameters include a modulation andcoding scheme (MCS) that is based on a Channel Quality Indicator (CQI)value in the calculated CSI for one of the selected CSI processes.

A non-transitory computer-readable storage medium that storesinstructions for execution by one or more processors to performoperations for reporting channel state information (CSI) in a cellularnetwork is also disclosed herein. The operations may configure a UE toreceive, in a first subframe, a first aperiodic CSI request from a firstcell group; receive, in the first subframe, a second aperiodic CSIrequest from a second cell group; determine a number of requested CSIprocesses corresponding to the first aperiodic CSI request and thesecond aperiodic CSI request; select a subset of the requested CSIprocesses when the determined number of requested CSI processes is morethan five; calculate CSI for the selected CSI processes; generate a CSIreport based on the calculated CSI for the selected CSI processes; andtransmit the CSI report to the first cell group and the second cellgroup.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims. The following claims are hereby incorporatedinto the detailed description, with each claim standing on its own as aseparate embodiment.

1. (canceled)
 2. An apparatus of a User Equipment (UE), the apparatuscomprising: memory; and processing circuitry, to: decode downlinkcontrol information (DCI) to configure the UE for aperiodic channelstate information (CSI) reporting using a physical uplink shared channel(PUSCH); decode radio-resource control (RRC) signaling from a mastercell group (MCG) associated with a master enhanced node B (MeNB), theRRC signaling to provide configuration information for configuring theUE with a secondary cell group (SCG) for dual connectivity to allow theUE to utilize radio resources of both the MCG and the SCG, the SCGassociated with a secondary eNB (SeNB); decode a subframe to determineif multiple aperiodic CSI report requests for the MCG and the SCGtrigger more than one CSI report; when five or less CSI reports aretriggered, update CSI for CSI processes corresponding to each of thetriggered CSI reports; when more than five CSI reports are triggered,update the CSI for CSI processes for at least five of the triggered CSIreports, wherein the UE is not required to update CSI for more than fiveof the CSI processes when configured with multiple cell groups; andperform CSI reporting for transmission on the PUSCH for the updated CSIfor the CSI processes, wherein the memory is configured to store theDCI.
 3. The apparatus of claim 2, wherein the subframe includes a valueassociated with a CSI request field comprising two bits, and wherein thevalue is one of a first predetermined value, a second predeterminedvalue, a third predetermined value, and a fourth predetermined value. 4.The apparatus of claim 3, wherein: the first predetermined value is“00”; the second predetermined value is “01”; the third predeterminedvalue is “10”; and the fourth predetermined value is “11”.
 5. Theapparatus of claim 2, wherein the processing circuitry is furtherconfigured to: perform first CSI reporting corresponding to a firstaperiodic CSI request from the MCG in the multiple aperiodic CSIrequests; and perform second CSI reporting corresponding to a secondaperiodic CSI request from the SCG in the multiple aperiodic CSIrequests.
 6. The apparatus of claim 5, wherein the processing circuitryis further configured to: encode a first CSI report corresponding to thefirst CSI reporting for transmission to the MCG on the PUSCH; and encodea second CSI report corresponding to the second CSI reporting fortransmission to the SCG on the PUSCH.
 7. A non-transitorycomputer-readable storage medium that stores instructions for executionby one or more processors of a User Equipment (UE) to performoperations, the operations to configure the one or more processors to:decode downlink control information (DCI) to configure the UE foraperiodic channel state information (CSI) reporting using a physicaluplink shared channel (PUSCH); decode radio-resource control (RRC)signaling from a master cell group (MCG) associated with a masterenhanced node B (MeNB), the RRC signaling to provide configurationinformation for configuring the UE with a secondary cell group (SCG) fordual connectivity to allow the UE to utilize radio resources of both theMCG and the SCG, the SCG associated with a secondary eNB (SeNB); decodea subframe to determine if multiple aperiodic CSI report requests forthe MCG and the SCG trigger more than one CSI report; when five or lessCSI reports are triggered, update CSI for CSI processes corresponding toeach of the triggered CSI reports; when more than five CSI reports aretriggered, update the CSI for CSI processes for at least five of thetriggered CSI reports, wherein the UE is not required to update CSI formore than five of the CSI processes when configured with multiple cellgroups; and perform CSI reporting for transmission on the PUSCH for theupdated CSI for the CSI processes.
 8. The non-transitorycomputer-readable storage medium of claim 7, wherein the subframeincludes a value associated with a CSI request field comprising twobits, and wherein the value is one of a first predetermined value, asecond predetermined value, a third predetermined value, and a fourthpredetermined value.
 9. The non-transitory computer-readable storagemedium of claim 7, wherein the subframe includes a value associated witha CSI request field comprising two bits, and wherein the value is one of“00”, “01”, “10”, and “11”.
 10. The non-transitory computer-readablestorage medium of claim 7, the operations to further configure the oneor more processors to: perform first CSI reporting corresponding to afirst aperiodic CSI request from the MCG in the multiple aperiodic CSIrequests; and perform second CSI reporting corresponding to a secondaperiodic CSI request from the SCG in the multiple aperiodic CSIrequests.
 11. The non-transitory computer-readable storage medium ofclaim 10, the operations to further configure the one or more processorsto: encode a first CSI report corresponding to the first CSI reportingfor transmission to the MCG on the PUSCH; and encode a second CSI reportcorresponding to the second CSI reporting for transmission to the SCG onthe PUSCH.
 12. An apparatus of a User Equipment (UE) configurable fordual connectivity, the apparatus comprising: memory; and processingcircuitry, to: decode downlink control information (DCI) to configurethe UE for aperiodic channel state information (CSI) reporting using aphysical uplink shared channel (PUSCH); decode radio-resource control(RRC) signaling from a master cell group (MCG) associated with a masterenhanced node B (MeNB), the RRC signaling to provide configurationinformation for configuring the UE with a secondary cell group (SCG) fordual connectivity to allow the UE to utilize radio resources of both theMCG and the SCG, the SCG associated with a secondary eNB (SeNB); decodea subframe including a value associated with a CSI request field todetermine if multiple aperiodic CSI report requests for the MCG and theSCG trigger more than one CSI report, wherein the memory is configuredto store the subframe; when five or less CSI reports are triggered,update CSI for CSI processes corresponding to each of the triggered CSIreports; when more than five CSI reports are triggered, update the CSIfor CSI processes for at least five of the triggered CSI reports,wherein the UE is not required to update CSI for more than five of theCSI processes when configured with multiple cell groups; and perform CSIreporting for transmission on the PUSCH for the updated CSI for the CSIprocesses.
 13. The apparatus of claim 12, wherein the CSI request fieldcomprises two bits, and wherein the value is one of a firstpredetermined value, a second predetermined value, a third predeterminedvalue, and a fourth predetermined value.
 14. The apparatus of claim 13,wherein: the first predetermined value is “00”; the second predeterminedvalue is “01”; the third predetermined value is “10”; and the fourthpredetermined value is “11”.
 15. The apparatus of claim 12, wherein theprocessing circuitry is further configured to: perform first CSIreporting corresponding to a first aperiodic CSI request from the MCG inthe multiple aperiodic CSI requests; and perform second CSI reportingcorresponding to a second aperiodic CSI request from the SCG themultiple aperiodic CSI requests.
 16. The apparatus of claim 15, whereinthe processing circuitry is further configured to: encode a first CSIreport corresponding to the first CSI reporting for transmission to theMCG on the PUSCH; and encode a second CSI report corresponding to thesecond CSI reporting for transmission to the SCG on the PUSCH.
 17. Theapparatus of claim 16, wherein the UE is configured to: transmit thefirst CSI report to the MCG on the PUSCH; and transmit the second CSIreport to the SCG on the PUSCH.